12 Letter Countable Nouns Starting with O

Explore 86 verified English 12 letter countable nouns that start with O, including Organization, Optimization, Overreaction, Officeholder, Orthodontist, Overestimate and Obliteration. Browse these count nouns with singular and plural forms below, or review singular and plural count rules in our noun grammar guide.

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Starts with OB6 words
obliteration
obstetrician
obscurantist
obedientiary
obnubilation
obsessionist
Starts with OC5 words
octogenarian
octosyllabic
oceanologist
octosyllable
ochlophobiac
Starts with OD5 words
odontologist
odontophobia
odontography
odontophoran
odontopteryx
Starts with OF
1 words
officeholder
Starts with OL5 words
oligopeptide
oleochemical
olallieberry
oleandomycin
olfactometer
Starts with OM
2 words
ombudsperson
omnishambles
Starts with ON6 words
onomatopoeia
oneirocritic
oneiromancer
oncornavirus
onomastician
onychophoran
Starts with OO
1 words
oophorectomy
Starts with OP10 words
optimization
operatorship
opsonization
opisthotonos
operationist
ophidiophile
ophidiophobe
opisthograph
ophiophilist
opisthodomos
Starts with OR12 words
organization
orthodontist
orchestrator
orchardgrass
ornithomimid
orchidectomy
organologist
ornithogalum
orthographer
orthopteroid
orthopterist
ornithomorph
Starts with OS9 words
oscilloscope
ossification
osteosarcoma
oscillograph
osteospermum
osteichthyan
osteopathist
osteoglossum
osteoglossid
Starts with OT
1 words
otosclerotic
Starts with OU
1 words
outmigration
Starts with OV21 words
overreaction
overestimate
overachiever
overexposure
overemphasis
overexertion
overactivity
overcapacity
overanalysis
overpressure
overtrousers
overpainting
overstanding
overoptimist
oversubtlety
overissuance
overdelicacy
ovariotomist
overkindness
overdiscount
overflourish
Starts with OX
1 words
oxaloacetate

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